What a coinky-dink - JSchmitz asked this in the CB not more than a day ago. If you're looking to trap the Ctrl-z which suspends a process then you need to trap the TSTP signal e.g

shell> perl -e '$SIG{TSTP} = sub { warn "suspension trapped\n" }; \
                sleep 50; print "on with the show ...\n"'

__output__

suspension trapped
on with the show ...
[download]

That of course assumes Ctrl-z was pressed within those 50 sleeping seconds. Also note that this interrupts the current operation, in this case the sleep (at least on my linux system). Check out man 7 signal for more info on signals.
HTH

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broquaint